Patients suffering from injury or disease or recovering from surgery may be treated by the application of constant or intermittent pressure. Pressure is used to control swelling, increase blood flow, and immobilize tissue.
In cases of acute injuries, such as acute joint injury, three treatments are employed simultaneously. First, the injured region is chilled (such as with ice); second, pressure is applied using an elastic bandage; and third, immobilization is achieved using a splint. For example, an athletic trainer applies elastic wrap to an injured ankle or knee and then immobilizes the joint with a splint or bulky bandage. However, the application of elastic wrap may produce a wide range of pressures on the injured limb. The incorrect pressure may retard venous or arterial circulation and may contribute to thromboembolism; pressure that is too high can induce tissue ischemia that further injures the tissue.
More complex pressure devices are available to patients suffering from various venous, circulatory and peripheral vascular diseases. These devices typically consist of an inflatable bladder in the form of a sleeve that can be placed around all or a portion of a patient's arm or leg. The bladder is connected to a pump that alternately inflates and deflates the bladder. In some such devices, the sleeve placed around the extremity includes a number of sequential bladders along the axial length of the sleeve to allow the sleeve to be inflated and deflated in a peristaltic manner along its length. By alternately inflating and deflating the bladder or bladders contained within the sleeve, circumferential pressure is applied to the patient's extremity, thus aiding in the circulation of blood there through. Such systems are currently used to treat venous insufficiency, prevent deep venous thrombus and control lymphedema and improve tissue perfusion in patients with peripheral arterial disease.
Other medical devices such as catheters and tracheotomy tubes are placed into a body lumen and then held in place with an inflatable balloon at the distal end of the device. The balloon is subject to over-inflation, however, again resulting in possible damage to treated tissue.
In addition, current systems tend to be expensive and complex, frequently being coupled to feedback circuits to control changes in pressure. Compression systems have been known to malfunction and cause undesirable variability in or increase in the applied pressure. Even when such systems are controlled by the patient, they may be subject to incorrect operation resulting in over-inflation of the sleeve. For such a system used to correct venous insufficiency in a limb, for example, incorrect operation is at best painful and at worst results in loss of the limb. Finally, most patients complain of some level of pain during inflation due to the rapid increase in pressure against the extremity.
In view of the above, the need exists for therapeutic devices that are capable of applying pressure but which are unable to produce over-pressure at the site of damage or disease. Such devices should be simple to use, allow peristaltic pumping at a variety of pressures, and have the ability to apply heat or cold.